Add a new version of Rolling Sum and Rolling Average (RPSUM and RPAVG)

Recently, we were trying to create a widget using the RPAVG function for a rolling 30-day average, which broke our connection to the live model while working (to an extent) on an elasticube. The function worked past the first 30 days on the elasticube, while the first thirty days were (SUM N )/ N. This formula works past those thirty days, but for the first value, for example, gives simply the first value.  A new version of these functions would be greatly appreciated.